This invention generally relates to semiconductor devices, and more specifically to preventing unauthorized use of integrated circuits for radiation-hard applications. Even more particularly, embodiments of the invention relate to preventing such unauthorized use of integrated circuits formed using a silicon-on-insulator technology.
Silicon-on-insulator (SOI) technology refers to the use of a layered silicon-insulator-silicon substrate in place of conventional silicon substrates in semiconductor manufacturing to reduce parasitic device capacitance, thereby improving performance. SOI based devices are an improvement on the earlier bulk Si metal oxide semiconductor (CMOS) technology.
SOI based devices differ from earlier bulk silicon-built devices in that the thin silicon junction is above an electrical insulator such as silicon dioxide.
SOI technology is one of a number of manufacturing improvements that enable the continued miniaturization of microelectronic devices. SOI substrates may be fabricated in ways that are compatible with many standard semiconductor manufacturing methods. SOI based devices may be fabricated without special equipment or substantial re-tooling of existing semiconductor manufacturing equipment.
One advantage of SOI based devices is that they are much less susceptible to errors induced by radiation than are bulk Si CMOS based devices. These errors are often typically referred to as soft errors.
Partially depleted SOI (PDSOI) circuits are significantly immune to soft errors. In the past, PDSOI MOSFETs were sensitive to total ionizing dose (TID) effects. However, with the relatively high doping density used in the channels of PDSOI devices, for example on 45 and 32 nm node, these device are almost completely insensitive to TID.
Although reducing the likelihood of soft errors is, in general, an advantage, there are disadvantages of or restrictions on products with a high resistance to radiation. For example, there are government restrictions on the sale and export of semiconductor circuits having radiation resistance characteristics that meet or exceed specified levels. Such semiconductor products are referred to as radiation-hardened.
It is possible to use a circuit fabricated in an advanced commercial PDSOI technology in radiation-hard applications. So, there is a need for a method and system to prevent potential unauthorized use.